Effects of B4C on the microstructure and phase transformation of porous SiC ceramics

Porous SiC ceramics sintered with B4C additive exhibit excellent corrosion resistance in hot acidic and basic solutions compared with traditional porous ceramic membrane supports. The effects of B4C on the density, phase composition, and microstructure of porous 6H–SiC ceramics were investigated in this study. The phase composition and microstructure of the as-prepared samples were characterized through X-ray diffraction, Raman spectrum, scanning electron microscopy, and electron probe microanalyzer equipped with wavelength dispersive spectrometry. B4C promoted the sintering of porous SiC ceramics within the temperature range of 2100–2200 °C. The B4C content higher than 0.5 wt% induced the phase transformation of 6H–SiC to 4H–SiC at 2200 °C, resulting in the formation of large plate-like 4H–SiC grains, which significantly improved the flexural strength of the porous ceramics. The mechanisms of phase transformation and grain formation were also elucidated.